1. Field of the Invention
The present invention relates to grinding of small pieces of sheet glass, for the purpose of shaping of the pieces to be fit into an assembly such as, for example, art works popularly known as stained glass.
2. Description of the Prior Art
Shaping of small pieces of glass to desired shapes, where these shapes include irregular wholly and partly curved peripheral boundaries, has conventionally been a laborious process requiring experience and skill on the part of the person shaping the glass. The process includes first inscribing a score corresponding to a desired outer peripheral boundary on a sheet of glass, then removing outlying unwanted glass to leave the remaining piece of glass in a desired final shape. The nature of glass renders removal of unwanted glass from the peripheral boundary difficult and tedious. A number of factors cause removal of unwanted glass to proceed in a manner which may be unintended and undesirable. For example, applying a bending moment along the score line may possibly not cause fracture to proceed along the score line. This may occur when surface irregularities and internal defects are present in the glass. Also, glass tends to fracture more or less in a straight line. These and other factors frequently cause the resulting peripheral boundary of a piece of glass being worked to depart from the original intended peripheral boundary.
In producing pieces of glass suitable for mounting using lead came and copper foil techniques, it is therefore desirable that the outer periphery of one piece of formed glass conform to a corresponding outer periphery of an adjacent section of glass. Moreover, it is desirable that the wall of a piece of formed glass be generally perpendicular to the flat major face of the glass. Therefore, despite taking steps such as forming curves in progressive steps of removal of glass and using grozing pliers to nibble away at peripheral boundaries, a piece of formed glass may take a form not suited to being placed in close proximity to an adjacent piece of glass.
The use of diamond grinding has advanced the art over purely manual methods but still is not fully reliable. Standard prior art practice is to start with a design drawn to full scale on paper. The design is transferred to heavier card stock paper. The card stock is cut along pattern lines using special three bladed scissors which remove a kerf while cutting the card stock into individual desired pattern pieces. The kerf accommodates lead came or copper foil which will separate adjacent pieces of cut glass, depending upon the method selected. The profile of each pattern piece is then inscribed upon stock glass. Typically, this is done by tracing each pattern piece in indelible ink marker. An alternative method is to adhere pattern pieces to glass using a water resistant rubber adhesive. Both methods of inscribing the pattern on the glass entail drawbacks.
One problem common to both approaches is that the three bladed scissors have severe difficulty in cutting curves. Also, when pattern pieces are cut from the master card, extreme care must be exercised to assure that the pieces be cut to reflect their actual location and spacing relative to the master design. This step is frequently not accomplished, with the consequence that the design increases in scale as cutting proceeds. Transference using indelible ink marking has the problem that if grinding is made to the edge of the ink line, the resultant piece will be slightly larger than desired. Adjacent finished glass pieces must then be spaced farther from their ideal locations, or else the gap separating adjacent glass pieces is too small. If grinding erodes the entire ink line, then the ground part will be too small and will fit poorly into the design. The ink line is also subject to being expunged from the glass by action of the glass shavings slurry produced during grinding. The approach of using a paper template adhered to the glass also suffers from the problem that edges of the paper card stock soften when moistened, and become subject to distortion by the operator""s fingers as grinding proceeds. Finally, it is frequently difficult to discern precise location of the grinding surface relative to the pattern marking because the grinding wheel is coated with the glass shavings slurry.
Problems inherent in traditional methods of glass shaping include breakage and redundant attempts to form difficult shapes, loss of time, breakage, and necessity for skilled craftsmanship. There exists in the prior art a need for improved shaping of glass pieces.
The present invention sets forth improvements which enable those of more ordinary skill to grind desired shapes into glass pieces with greater precision and reduced reliance upon breaking away sections using scores. Additionally, the problems relating to conventional diamond grinding are substantially overcome. The invention utilizes a water resistant translucent or transparent mask material bearing an opaque outer periphery to locate the edge of the desired pattern on the glass. Transparency of the mask enables the pattern to be traced directly onto the mask, rather than using the cumbersome prior art practice of interposing carbon paper between the master pattern and the card stock material used as a mask. The novel mask is cut by conventional two bladed scissors, which can cut along curves, rather than using the traditional three bladed scissors which form a kerf. The novel mask, being water resistant, is not distorted by handling in a wet environment.
The periphery of the design on the mask is darkened or otherwise made to contrast visually with untreated portions of the glass, so that the desired pattern is immediately and readily discerned. This treatment of the glass work piece becomes more effective when taken in conjunction with a modification to the diamond grinding apparatus wherein backlighting is introduced thereto. In this modification, the diamond grinding machine is provided with lamps arranged to provide backlighting which will bring the darkened or preferably opaque outer periphery of the pattern into clear view despite fouling from the glass shavings slurry. Bearing in mind that most glass pieces being ground are usually colored, it will be appreciated that prior to grinding, a strongly colored, strongly illuminated zone of excess glass to be removed exists between the grinding surface and the opaque outer periphery of the mask. The operator of the diamond grinder is thus afforded clearly discernible indication of material still to be removed.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. This and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.